Quat T. Vu

Encapsulated copper interconnection devices using sidewall barriers

The concept of treating interconnections as a device and designing them while keeping both materials and structures in mind is presented. An example using molybdenum and copper is demonstrated. Copper introduces new problems such as diffusion in addition to the traditional problems for interconnections such as adhesion. A new structure called a sidewall barrier is used as part of a copper interconnection. This structure can be combined with a multilayer thin film resulting in a completely encapsulated interconnection. The technique is versatile enough that almost any material including dielectrics can be used as the encapsulation material and the sidewall barrier can be either on the outside of a feature or the inside of a space. Several potential metals (Mo, TiN, W) for encapsulating copper are examined and molybdenum is chosen and used. Both sputtering and switched-bias sputtering are used to deposit molybdenum sidewall barriers followed by anisotropic etching for patterning. Electromigration measurements of bilayered copper films reveal that there are problems with TiN and tungsten barriers. Copper oxidation, stress, electromigration, hillock growth, resistivity, diffusion and adhesion are all studied.

T-Matrix De-Embedding of IC Metal Transmission Lines to 18 GHz

T-matrix methods are applied to S-parameter data from on-chip metal lines connected to microwave measurement equipment so as to preserve mirror symmetry in the entire system. The propagation constant ¿ and characteristic impedance Zin of a line are derived from measurements on two different lengths of line. It is shown here that Zin can be found with few assumptions about the transition networks. In particular, we present a theorem for determining Zin or its phase for any symmetric or lossless transition network. Multiple lengths of otherwise identical IC line allow redundant, pairwise solutions to be acquired, with high confidence in the final result. Experimental results show that todays IC metal lines at Intel can have flat R, L, G, and C to at least 18 Ghz.